I found out recently that one of the all-time classic book in computer science, Structure and Interpretation of Computer Programs, is available in ePub format for free.  The book is truly a classic but has been out of print for a long time now.

For those unfamiliar with the text, from Amazon’s site:

Abelson and Sussman’s classic Structure and Interpretation of Computer Programs teaches readers how to program by employing the tools of abstraction and modularity. The authors’ central philosophy is that programming is the task of breaking large problems into small ones. The book spends a great deal of time considering both this decomposition and the process of knitting the smaller pieces back together.

The authors employ this philosophy in their writing technique. The text asks the broad question “What is programming?” Having come to the conclusion that programming consists of procedures and data, the authors set off to explore the related questions of “What is data?” and “What is a procedure?”

The authors build up the simple notion of a procedure to dizzying complexity. The discussion culminates in the description of the code behind the programming language Scheme. The authors finish with examples of how to implement some of the book’s concepts on a register machine. Through this journey, the reader not only learns how to program, but also how to think about programming.

The contents of the book are timeless and give computer scientists young and old a solid level of knowledge.  It uses Scheme, a dialect of Lisp, but that should not deter readers as the lessons are universal.

The full text is also available to be read online for those not able to read in ePub format.  Great stuff!